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(meteorobs) Meteor Activity Outlook for Mar 26-April 1, 2004

The moon reaches its first quarter phase on Sunday March 28. At this time
the moon lies ninety degrees east of the sun and will set near midnight. As
the week progresses the moon will set later in the morning and will start to
interfere with observations toward dawn. The estimated total hourly rates
for evening observers this week should be near one for those in the Northern
Hemisphere and two for those south of the equator. For morning observers the
estimated total hourly rates should be near eight for those located in the
Northern Hemisphere and eighteen for those in the Southern Hemisphere. Rates
are reduced during the evening hours due to moonlight. These rates assume
that you are watching from rural areas away from all sources of light
pollution. The actual rates will also depend on factors such as personal
light and motion perception, local weather conditions, alertness and
experience in watching meteor activity.

The radiant positions listed below are exact for Saturday night/Sunday
morning March 27/28. The radiants do not change greatly day to day so the
given positions may be used during this entire period. Most star atlases
(available at science stores and libraries) will provide maps with grid
lines of the celestial coordinates so that you may find out exactly where
these positions are located in the sky. A planisphere or computer
planetarium program is also useful in showing the sky at any time of night
on any date of the year. Activity from each radiant is best seen when it is
positioned highest in the sky, either due north or south along the meridian,
depending on your location. Meteor activity is not seen from radiants that
are located below the horizon. The positions below are listed in a west to
east manner in order of right ascension (celestial longitude). The positions
listed first are located further west therefore are accessible earlier in
the night while those listed last rise later in the night. This list also
provides the order of ascending velocity for each radiant with those listed
first usually being much slower than those last on the list. Velocity should
not be the prime factor for shower association as all showers can produce
slow meteors. Slow meteors can be produced from normally swift showers, such
as the Leonids, when meteors appear near the radiant or close to the
horizon. The true velocity is only revealed in shower members seen far from
the radiant and high in the sky.

The Antihelion radiant is now centered at 13:24 (201) -08. This area of the
sky is located in central Virgo, three degrees north of the first magnitude
star Spica (Alpha Virginis). Since this radiant is large and diffuse, any
slow to medium speed meteor from northern Corvus, southwestern Bootes or
central Virgo could be a candidate for this shower. The center of this area
is best placed near 0100 local standard time when it lies on the meridian
and is highest in the sky. At this time expect to see two shower members per
hour regardless of your location.

Unlike most of the annual showers the antihelion source is produced by
debris from unknown objects orbiting in a direct motion like the earth.
These objects are most likely asteroids, which produce stony and metallic
debris whose density is much greater than material produced by comets. This
material collides with the earth on the inbound portion of its orbit, before
its closest approach to the sun. Therefore we best see them just after
midnight when we are facing the direction from which this activity appears.
The antihelion source is active all year from an area of the sky nearly
opposite that of the sun. The center of this source will move approximately
one degree eastward per day and travels through many different
constellations over the course of a year. It may make sense to list these
meteors as antihelions or "ANT" but a majority of meteor organizations
prefer that you list them from the constellation in which the radiant is
currently located or the constellation where the shower reaches maximum
activity. Those who send their data to the International Meteor Organization
should call these meteors Virginids (VIR).

The Northern Apex radiant is now centered at 18:24 (276) -08. This position
lies on the Scutum/Serpens Cauda border, five degrees northeast of the
fourth magnitude star Nu Ophiuchi. This area of the sky is best placed for
viewing during the last dark hour before dawn when it lies highest in the
sky. Since this radiant is large and diffuse, any meteor from eastern
Ophiuchus, southern Serpens Cauda, or Scutum could be a candidate from this
source. Rates would be now close to two per hour regardless of your
location.

Like the antihelion area, both apex areas are active all year long and
travel approximately one degree eastward per day. Unlike the antihelion
debris, these particles orbit the sun in a retrograde motion opposite that
of the earth and are most likely produced by unknown comets. They strike the
earth after their closest approach to the sun. Since they are moving in
opposite directions these particles strike the earth at tremendous
velocities often creating bright meteors with persistent trains. These
particles strike the earth on the morning side of earth and are best seen
just before morning twilight while the sky is still perfectly dark. This is
not really a "shower" per se, but an artificial radiant created by the
Earth's motion through space. Meteors from both branches are normally
included in the sporadic count. I feel it is a worthy project to see if it
is possible to distinguish these meteors from the normal sporadic
background. On rare occasions there are meteors with a zero inclination that
radiate precisely from the apex point on the ecliptic, exactly 90 degrees
west of the sun. In simplistic terms, these meteors are seldom seen since
the Earth "sweeps clean" much of the material that shares the same orbit as
our planet. Much more material is located just north and south of the
earth's orbit with slightly higher or lower inclinations. This creates the
northern and southern branches of the apex activity.

The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 18:24 (276) -38. This position lies in the northern Corona
Australis, very close to the third magnitude star Eta Sagittarii. Like the
northern apex, these meteors are best seen toward dawn when the radiant lies
highest above the horizon in a dark sky. Since this radiant is also large
and diffuse, any meteor from northwestern Corona Australis, southwestern
Sagittarius or southeastern Scorpius could be a candidate from this source.
Rates would now be less than one per hour in the Northern Hemisphere and two
per hour in the Southern Hemisphere.

The Delta Pavonids (DPA) are listed among the radiants of the Dutch Meteor
Society. They are predicted to peak on March 28. The radiant currently lies
at 20:32 (308) -63. This area of the sky is located in central Pavo, four
degrees northwest of the third magnitude star Beta Pavonis. This area of the
sky is too far south to be seen north of the northern equatorial areas. The
ZHR at maximum is five shower members per hour. These rates are rarely seen
except from far southern locations such as Australia, South Africa and
southern South America.  The best time to view this activity is just before
the start of morning twilight, when the radiant lies highest in a dark sky.
With an entry velocity of 60 kilometers per second, a majority of these
meteors will appear to move swiftly.

The Sporadic rates for the Northern Hemisphere are declining. One would
currently expect to see perhaps four random meteors per hour during the last
hours before dawn from rural observing sites. This estimate and the morning
estimate for the Southern Hemisphere do not include the apex meteors listed
above. During the evening hours perhaps two random meteors can be seen per
hour from the Northern Hemisphere. Rates seen from the Southern Hemisphere
are now stronger than those seen in the northern skies with perhaps seven
random meteors being seen per hour during the early morning hours and three
per hour during the evening.

Clear Skies!
Robert Lunsford
AMS Operations Manager

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